Production of passive restraint device

ABSTRACT

An elastomer-coated fabric for use as a confinement. The confinement is formed by conforming a fabric to a mold having the shape of the desired confinement, and subsequently applying a layer of elastomer to the fabric. A curing operation then cures the elastomer such that the elastomer-coated fabric retains the shape of the mold. Advantageously, the curing operation also relaxes and heat sets the fabric in order to permit a controlled amount of further stretch, even if the fabric was stretched a maximum amount when it was conformed to the mold.

FIELD OF THE INVENTION

The present invention relates generally to the formation of fabricconfinements and more particularly to the formation of a moldedelastomer-coated fabric air restraint bag.

BACKGROUND OF THE INVENTION

Much attention has recently been directed to the formation of fabricconfinements requiring special characteristics. For example, theautomobile industry has become increasingly concerned with safety ofautomobile occupants during a crash. It is known to construct aconfinement, referred to as an "air bag" in an automobile which isinflated upon detection of a crash. Today, many automobile manufacturershave met consumer concern for safety through the inclusion of air bagsin motor vehicles not only as optional equipment but also as standardequipment.

However, manufacturers have encountered difficulty and expense in theformation and production of air bags of specified shapes and dimensions.

A typical air restraint system presently utilized in passenger motorvehicles includes an inflatable confinement, or air bag, an impactdetector and an inflating means. Upon detection of an impact greater inmagnitude than a threshhold impact, the impact detector provides asignal to the inflating means which causes the inflating means toinflate the confinement. The inflating means illustratively comprises apyrotechnic or gas producing means. Thus, the inflated confinementserves to protect the passenger and/or driver from what is oftenconsidered the most serious effect of an automobile collision--asecondary collision, i.e., the collision between an occupant and theinterior of the motor vehicle.

Unfortunately, any such air restraint system is effective in preventingpersonal injury only to the extent that the occupant properly contactsthe inflated bag. Thus, the dimensions and shape of an inflated air bagare critical and are often dictated by an exacting specification.

The specific shape and dimensions of any particular air bag are affectedby the position in which it is placed in a motor vehicle. Considerationmust be given to not only the position of the protected occupant(s) butalso to the portion of the vehicle's interior in close proximity to theair bag and against which the air bag will be forced in a collision.Such design considerations, among others, have led to uniquely shapedair bags. For example, U.S. Pat. No. 4,262,931 to Strasser et al.discloses an air bag having a plurality of compartments for knee, torsoand head restraint, some of which deploy towards one of the passengerseating positions and some of which expand laterally across the vehicleinterior in front of the adjacent passenger position. This particulardevice also utilizes a pressure regulating valve flap betweencompartments. U.S. Pat. No. 3,937,488 to Wilson et al. depicts anelongated air bag of approximately rectangular cross-section and planarend sections. This particular device utilizes two different materials ofdifferent air permeability to form the air bag.

Some known devices have attempted to solve problems associated withproviding air bags of precise shapes and dimensions through stitchingtogether separate sheets of fabric so as to form a desired shape.Unfortunately, stitched seams in known air bags have encountereddifficulty in maintaining the pressure within the bag during inflation.Air bags, in order to be effective, must inflate within a fraction of asecond. Such a rapid rate of inflation leads to the exertion of atremendous tensile load on the stitching. Such stitching decreases theoverall strength of the fabric at the seam due to the perforations inthe fabric inherent from the stitching process. Additionally, thestrength of the stitching thread must be considered, as well as theadditional cost of stitching.

Furthermore, stitching of separate sheets of fabric, whether they areidentical or of different air permeability, increases the bulk of theair bag, as the seam will have a thickness which is at very least thesum of the thickness of both separate sheets of fabric. With the currentpractice of downsizing vehicles, any unnecessary bulk is mostundesirable. Stitching is also undesirable since it produces aprotrusive stitched surface which may harm an occupant whom it contacts.Illustrative of air bags constructed from stitched together layers offabrics is that disclosed in U.S. Pat. No. 3,892,425 to Sakairi et al.

For the sake of completeness, it has been recognized that air restraintbags which at least partially deflate soon after, or even during,inflation advantageously provide a means to counteract the dangerouseffect known as rebound. Such controlled deflation permits the air bagto absorb more energy from the occupant.

Various methods have been proposed for the controlled deflation of airbags. Illustrative of such methods are those disclosed in U.S. Pat. Nos.3,937,488 to Wilson (air bag constructed from at least two materialshaving different air permeability values) and 3,892,425 to Sakairi etal. (air bag constructed from coated material wherein expansion of theair bag stretches the stitches of the fabric, creating new openingsthrough the coating in addition to microporous openings).

Additionally, the exacting specifications to which an air bagmanufacturer must adhere to include requirements relating to shape,dimension, energy absorption, inflation and deflation time periods,toxicity, flammability, temperature and accelerated aging resistance.Unfortunately, the use of coated fabrics can present difficult inmeeting such requirements.

SUMMARY OF THE INVENTION

This present invention relates to an air bag restraint system forprotecting an occupant of a vehicle during a collision comprising aninflatable confinement adapted for attachment to the vehicle andinflatable upon collision of the vehicle. The confinement is constructedfrom a seamless mold-formed elastomer-coated stretchable fabric. Such asystem also includes means for inflating the confinement with a fluidupon the occurrence of a collision. The inflating means inflates theconfinement to a predetermined shape upon a collision, the shape beingdetermined by characteristics of the mold-formed elastomer-coatedfabric. The elastomer coating is preferably cross linked andillustratively ranges in thickness from 0.5 to 10 mils.

The elastomer coating comprises any suitable material which renders thefabric essentially non-porous and non-permeable. Such materialpreferably has a sufficiently long shelf life and tends not to becomebrittle with age or temperature extremes. Additionally, in the eventthat pyrotechnic means are employed to inflate the confinement, theelastomer must be especially resistant to heat. Illustrative of suitablematerials are neoprene, nitrile, silicone, acrylic, urethane, polyvinylchloride (PVC), butyl, ethylene propylene diene monomer elastomers(EPDM), or a combination of these and/or other suitable materials.Additionally, coatings disclosed in U.S. Pat. No. 3,807,754 to Rodenbachet. al. which is incorporated herein by reference may be employed withthe present invention.

In one embodiment, the fabric is knit on production units such as whatis known in the art as "Tricot", "Rashel", "Simplex" or "Weft" machines.These illustrative machines produce a circular or "stocking-like"product in which bands of increasing or decreasing fabric density may beintroduced by increasing or decreasing the number of yarn ends in a tubeof the device.

The fabric is preferably knitted from a yarn having a filament or spunconfiguration which suitably enhances the fabric by elongating undertension and shrinking and/or relaxing when exposed to heat.

Advantageously, desired confinement configurations may be obtained byemploying non-uniform fabric density in the stocking-like confinement.Such non-uniform density allows, for example, a high degree of expansionin a body portion of the confinement and a low degree of expansion in aneck and a toe portion of the confinement, i.e., a reinforced neck andtoe portion.

The fabric provides resistance to tear and may be constructed of a widevariety of materials. Illustrative materials include cloth, plastic,metal, fiberglass or any other material which may be made to take on adesired shape. Preferably, the fabric is knitted so as to be stretchablein both a machine direction and a cross-machine direction so as toeasily conform to a desired shape. The fabric is relaxed and heat set topermit further stretch during inflation.

The inflatable confinement is preferably provided with means fordeflating operative during and/or after the inflating process so as toprevent rebound of the occupant engaging the confinement. The means fordeflating may comprise a plurality of ports through which the fluidflows outward.

The inflating means is provided to quickly inflate the confinementduring a collision and illustratively is a pressurized fluid orpyrotechnic system. Furthermore, the fluid utilized is preferably a gas.

The present invention also relates to an improved passive air restraintdevice of the type having an air bag inflatable upon a collision,inflating means to inflate the air bag upon the collision and collisiondetection means to detect a collision of magnitude at least equal to athreshhold magnitude, wherein the improvement comprises a seamless airbag formed from a stretchable fabric having thereupon an elastomercoating so as to render the fabric essentially non-porous andnon-permeable. Advantageously, the seamless air bag is deflatable andthen inflatable to a desired shape.

The present invention also relates to a method for manufacturing aninflatable confinement for use in protecting an occupant of a vehicleduring a collision, which method comprises providing a mold having anexterior surface forming a desired shape, conforming a stretchablefabric to the exterior surface of the mold, applying an elastomercoating to the fabric and heating the elastomer coating at a sufficienttemperature for a sufficient time to provide a cured elastomer-coatedfabric having a shape identical to the shape of the mold.Advantageously, the heating relaxes and heat sets the fabric so as topermit subsequent stretching of said elastomer-coated fabric. Thesubsequent stretching of the elastomer-coated fabric is approximatelyfrom three to twenty-five percent beyond the size of the mold upon whichit is heated and is brought about during operation of the device as thefluid rushes in to the confinement.

The step of conforming the stretchable fabric to the shape of the moldcomprises applying the fabric over an exterior surface of an at leastpartially deflated inflatable mold and inflating the mold to apredetermined size, thus stretching the fabric to take on the shape ofthe exterior surface of the mold. Once the curing operation is complete,the inflatable mold is deflated so as to facilitate removal of theelastomer-coated fabric from the mold.

The present invention also relates to a method of manufacturing aninflatable confinement for use in passive air bag restraint deviceswhich comprises applying a seamless knitted fabric stretchable in both amachine and a cross-machine direction onto an at least partiallydeflated inflatable mold, inflating the inflatable mold to apredetermined size having an exterior surface of a desired shape, thusstretching the fabric as the mold is inflated, applying an elastomercoating to the stretched fabric in an amount sufficient to render thestretched fabric essentially non-porous, curing the elastomer coating byheating to a predetermined temperature for a time sufficient to providea cured elastomer-coated stretchable fabric having and retaining a shapeidentical to the desired shape of the exterior surface of the mold, thecuring step also relaxing and heat setting the stretchable fabric so asto permit subsequent stretching of the elastomer-coated fabric duringinflation of the confinement in a collision, and deflating theinflatable mold so as to facilitate removal of the elastomer-coatedfabric from the mold.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a method and apparatus for protecting occupantsof vehicles during sudden impact by way of an inflatable confinementcomprising a fabric to which an elastomer coating has been applied,wherein the inflatable confinement is formed by application of thefabric over a mold followed by application of an elastomer layer to thefabric and subsequent curing of the elastomer.

More specifically, a mold is created in the shape of the desiredproduct. The mold may take on a variety of shapes, and may have complexportions such as concave areas. Furthermore, the mold is preferablycollapsible, so as to be easily removed from the cured product.Additionally, bladder type inflatable molds may be employed to formproducts of similar shapes but different dimensions. Alternatively,molds may be created from plaster of Paris, frangible materials,cardboard, or a wide variety of materials which can easily be made tobreak, dissolve, disintegrate, melt or the like so as to be separatedfrom the fabric and elastomer. Collapsible type molds such as thoseincorporating a double-umbrella type structure may also be employed inthe present invention. Such a double-umbrella type structureillustratively comprises, in collapsed form, a tubular shaped memberwhich has a number of struts connected by suitable fabric, similar to anumbrella. Upon extension of the struts, an open umbrella configurationis achieved. Advantageously, two such sets of struts are provided in anend to end fashion such that a suitable confinement configuration iscreated upon expanding the tubular shaped member and extending thestruts. In such an embodiment, the fabric is applied over the collapsedstructure which is then extended and coated with an elastomer and cured.Subsequent to curing, the mold is collapsed and the confinement removed.

However, it is not necessary for a mold to deform, disintegrate, etc.,depending on its shape and dimensions and the desired shape anddimensions of the finished product. If removal of the finished productfrom the mold can be accomplished without tearing the product, andwithout subjecting the product to undue force, a rigid mold is suitablefor use with the present invention.

At the time of application of the fabric the inflatable mold is at leastpartially deflated, i.e., not in its fully inflated state, so as tofacilitate application of the fabric. Once the fabric is applied, theinflatable mold is inflated and is in the shape of the desired endproduct, however, the mold is preferably inflated so as to be slightlysmaller than the desired end product so as to allow for stretch causedby the sudden inrush of fluid during the inflation process. The degreeto which the inflatable mold is deflated at the time of application ofthe fabric is partially determined by the amount of stretch to which thefabric may be subjected to during the inflation of the mold withouttearing or otherwise deforming the fabric. The neck, or collar, area ofthe confinement is not produced with a reduced size so as to properlymate with a mechanism used to join the confinement to the pyrotechnic orgas producing means employed to deploy the confinement. The degree towhich the inflated mold is smaller than the desired end product willdepend on the specific type and quantity of elastomer and fabric, thevelocity, quantity and flow of the fluid entering the confinement duringinflation, the type of deflation system employed, as well as otherfactors. Rigid mold sizes, and inflated mold sizes for the case of aninflatable mold, of approximately three to twenty-five percent less thanthe size of the desired end product have been successfully employed.

The fabric to be applied over the mold may be any suitable fabric whichconforms or may be made to conform to the shape of the mold. The term"fabric" as used herein is intended to include all materials suitablefor use in making inflatable confinements in accordance with theinvention. Illustratively, such fabrics may be constructed from cloth,plastic, metal, fiberglass and the like. Thus, knitted fabrics aregenerally preferable over woven fabrics, especially for complex shapes,since knitted fabrics are generally stretchable in the machine directionas well as in the cross-machine direction, unlike woven fabric. Typicalknitted fabrics are underwear and socks.

A preferred fabric is constructed from yarn or thread of natural,synthetic or regenerated fiber that has been knit into a configurationto allow stretch in both the machine direction and the cross-machinedirection. Fabric knit to have stretch of at least 150 percent in eachsuch direction has been found to be suitable for a wide variety ofmolds.

Although such fabric may be knit into a wide variety of shapes, a sockor sleeve shape is preferable since it is easily placed over andconforms to molds of a wide variety of shapes. A fabric of shape, size-and stretch suitable for placement over the mold without the formationof folds or voids is preferably employed.

Once the fabric is placed over the rigid or collapsible mold or,alternatively, once the fabric is placed over the at least partiallydeflated inflatable mold and the mold inflated, an elastomer coating isapplied to the fabric. Preferably, a sufficient amount of elastomer isapplied so as to render the fabric essentially non-porous andnon-permeable to air under typical operating conditions. Application ofthe elastomer coating may be effected by any of a number of known meanssuch as spraying the elastomer onto the fabric, dipping the fabric intothe elastomer or brushing the elastomer onto the fabric. Additionally,the mold upon which the fabric is placed may be rotated as the elastomeris applied.

Any elastomer having suitable properties for the construction of aspecific air bag in accordance with design specifications may beemployed. Broadly, suitable air bags may be constructed with elastomerssuch as appropriately compounded chlorinated rubber, silicone,fluorosilicone, polyvinyl chloride, acrylate, or urethane. If necessary,permeability of the air bag may be adjusted by adjusting the amount ofdeposited elastomer. A range of one-half mil to ten mils has been foundsuitable for elastomer thickness, with two to seven mils beingpreferable.

Upon application of the elastomer to the mold-supported fabric, theelastomer is cured by curing methods such as by the application of heat.Additionally, the elastomer may be cured by radiation curing, in whichthe elastomer is exposed to a prescribed type and dose of radiation.Radiation curing permits the use of short curing times and also promotesa uniform curing of the elastomer.

Advantageously, the curing operation serves not only to cure theelastomer, but also to relax and heat set the threads or yarn of thefabric such that the fabric may be stretched to a greater extent thanwithout such curing. In other words, even under circumstances in whichit is necessary to stretch the fabric to its limit so as to conform tothe mold shape, the fabric, once it has been relaxed and heat set by thecuring operation, may be further stretched without tearing the fabric.Thus, when the air bag is inflated by inflating means such as apyrotechnic or gas supply, the air bag will take on the dimensionsrequired by the specification.

Subsequent to the curing process, the air bag is removed from the moldby an appropriate method. If a rigid mold were employed, the air bag isstretched and removed from the mold, while if an inflatable mold wasemployed, the mold is first deflated and then the air bag is removed.Alternatively, a disintegratable or frangible rigid mold can be utilizedin which case the mold is first disintegrated, dissolved, broken, etc.and then the air bag is removed.

Upon removal of the air bag from the mold, the air bag is preferablyreversed such that the untreated side of the fabric is exposed so as toconform to typical specifications in the air bag industry.

The cured air bag is preferably provided with means for deflating suchthat the air bag may absorb more net energy from the impact of a person.If no such deflating means were provided, the energy absorbed by the airbag from the impact of a person would be momentarily stored in the airbag as potential energy in the form of increased air bag pressure, andthen expended in forcing the person away from the air bag with the sameviolent force with which he impacted the air bag and hence, rebound.

By providing means for controlling the deflation of the air bag, theenergy absorbed by the air bag from the impact of a person is releasedby the air bag, however, it is not released in a manner harmful to theperson. For example, the means for deflating may comprise ports in theair bag through which the fluid may escape as the person impacts the airbag. Any number of such ports as will properly absorb the energy ofimpact may be provided. Alternatively, a blowout patch or tear stripsuch as that disclosed in U.S. Pat. No. 3,451,693 to Carey whichenlarges as pressure within the air bag increases may be provided.

While it is apparent that the invention herein disclosed is wellcalculated to fulfill the objects above stated it will be appreciatedthat numerous modifications and embodiments may be devised by thoseskilled in the art, and it is intended that the appended claims coverall such modifications and embodiments as fall within the true spiritand scope of the present invention.

More specifically, the present invention is not limited to use inautomobiles. The elastomer coated fabric may be used as an inflatableconfinement for protecting persons in trains, planes, boats or any otherapplication requiring inflation of a confinement having specified shape.Furthermore, the specific type and quantity of elastomer applied to thefabric will depend on the desired shape, size and stretch of theconfinement.

What is claimed is:
 1. A method for manufacturing an inflatableconfinement for use in protecting an occupant of a vehicle during acollision, which method comprises:providing a mold having an exteriorsurface forming a desired shape; conforming a stretchable knitted fabricto said exterior surface of said mold, by applying said fabric over saidexterior surface of an at least partially deflated inflatable mold andinflating said mold to a predetermined size, thus stretching said fabricto take on said shape of said exterior surface of said mold;subsequently applying an elastomer coating to said fabric; and curingsaid elastomer coating at a sufficient temperature and for a sufficienttime to provide a cured elastomer-coated fabric having a shape identicalto said shape of said mold; wherein said heating step relaxes and heatsets said fabric so as to permit subsequent stretching of saidelastomer-coated fabric.
 2. The method of claim 1 which furthercomprises deflating said inflatable mold subsequent to said heating stepso as to facilitate removal of said elastomer-coated fabric from saidmold.
 3. The method of claim 1 wherein said subsequent stretching ofsaid elastomer-coated fabric is approximately from three to twenty-fivepercent beyond the size of said mold upon which it is cured.
 4. Themethod of claim 1 which further comprises selecting said elastomercoating from at least one of the group of neoprene, acrylic, silicone,nitrile, urethane, PVC, butyl and EPDM.
 5. The method of claim 1 whereinsaid knitted fabric is stretchable in both a machine direction and across-machine direction.
 6. The method of claim 1 wherein said fabric isof a stretchable metal, plastic or fiberglass structure.
 7. A method ofmanufacturing an inflatable confinement for use in passive air bagrestraint devices, which method comprises:applying a seamless knittedfabric stretchable in both a machine and a cross-machine direction ontoan at least partially deflated inflatable mold; inflating saidinflatable mold to a predetermined size having an exterior surface of adesired shape, thus stretching said fabric as said mold is inflated;applying an elastomer coating to said stretched fabric on said mold inan amount sufficient to render said stretched fabric non-porous; curingsaid elastomer coating at a predetermined temperature for a timesufficient to provide a cured elastomer-coated stretchable fabric havingand retaining a shape identical to said desired shape of said moldexterior surfaces, said curing step also relaxing and heat setting saidstretchable fabric so as to permit subsequent stretching of saidelastomer-coated fabric during inflation of said confinement in acollision; and deflating said inflatable mold so as to permit removal ofsaid elastomer-coated fabric from said mold.
 8. The method of claim 7wherein said fabric is of a stretchable metal, plastic or fiberglassstructure.
 9. A method for manufacturing an inflatable confinement foruse in protecting an occupant of a vehicle during a collision, whichmethod comprises:providing a mold having an exterior surface forming adesired arcuate shape; conforming a stretchable knitted fabric to saidexterior surface of said mold in a manner to provide bands of increasingor decreasing fabric density depending upon the shape of said mold,wherein said conforming said stretchable fabric comprises applying saidfabric over said exterior surface of an at least partially deflatedinflatable mold and inflating said mold to a predetermined size, thusstretching said fabric to take on said shape of said exterior surface ofsaid mold; subsequently applying an elastomer coating to said fabric;and curing said elastomer coating at a sufficient temperature and for asufficient time to provide a cured elastomer-coated fabric having ashape identical to said shape of said mold; wherein said curing steprelaxes and heat sets said fabric so as to permit subsequent stretchingof said elastomer-coated fabric.
 10. The method of claim 9 which furthercomprises deflating said inflatable mold subsequent to said heating stepso as to facilitate removal of said elastomer-coated fabric from saidmold.
 11. The method of claim 9 wherein said subsequent stretching ofsaid elastomer-coated fabric is approximately from three to twenty-fivepercent beyond the size of said mold upon which it is cured.
 12. Themethod of claim 9 which further comprises selecting said elastomercoating from at least one of the group of neoprene, acrylic, silicone,nitrile, urethane, PVC, butyl and EPDM.
 13. The method of claim 9wherein said knitted fabric is stretchable in both a machine directionand a cross-machine direction.
 14. The method of claim 9 wherein saidfabric is of a stretchable metal, plastic or fiberglass structure.
 15. Amethod of manufacturing an inflatable confinement for use in passive airbag restraint devices, which method comprises:providing a mold of apredetermined size and having an exterior surface of a desired shape;applying a knitted fabric onto said exterior surface of an at leastpartially deflated inflatable mold and inflating said mold to apredetermined size, thus stretching said fabric to take on said shape ofsaid exterior surface of said mold; subsequently applying an elastomercoating to said fabric in an amount sufficient to render said stretchedfabric non-porous; curing said elastomer coating by heating to apredetermined temperature for a time sufficient to provide a curedelastomer-coated stretchable fabric having and retaining a shapeidentical to said desired shape of said mold exterior surfaces, saidcuring step also relaxing and heat setting said stretchable fabric so asto permit subsequent stretching of said elastomer-coated fabric duringinflation of said confinement in a collision; and removing theinflatable confinement from said mold.
 16. The method of claim 15wherein said removal step includes deflating said mold so as to permitremoval of said elastomer-coated fabric from said mold.
 17. The methodof claim 15 wherein said removal step includes collapsing said mold soas permit removal of said elastomer-coated fabric from said mold. 18.The method of claim 15 wherein said removal step includes disintegratingsaid mold so as to permit removal of said elastomer-coated fabric fromsaid mold.
 19. The method of claim 15 which further comprises selectingsaid elastomer coating from at least one of the group of neoprene,acrylic, silicone, nitrile, urethane, PVC, butyl and EPDM.
 20. Themethod of claim 15 which further comprises selecting said stretchablefabric of a knitted construction which is stretchable in both a machinedirection and a cross-machine direction.
 21. The method of claim 15wherein said fabric is of a stretchable metal, plastic or fiberglassstructure.